Daniele Baraldi | Università Iuav di Venezia (original) (raw)

Papers by Daniele Baraldi

Engineering Analysis with Boundary Elements, 2018

Journal of Engineering Mechanics, 2017

AbstractIn this work, a simple and effective finite element-boundary integral equation (FE-BIE) a... more AbstractIn this work, a simple and effective finite element-boundary integral equation (FE-BIE) approach for the static analysis of elastic beams and frames in bilateral frictionless contact with a...

Nelle analisi dinamiche di strutture in cemento armato vengono solitamente adottati legami ciclic... more Nelle analisi dinamiche di strutture in cemento armato vengono solitamente adottati legami ciclici che trascurano la resistenza a trazione del calcestruzzo e non considerano il ramo di ricarico da trazione verso compressione. Tuttavia tale approssimazione può condurre a risultati poco veritieri in quanto l’energia dissipata nei cicli isteretici può essere significativamente sottostimata. Ad esempio i diagrammi momento-curvatura di pareti snelle che adottano leggi cicliche del calcestruzzo di sola compressione presentano cicli isteretici a forma di “bandiera”. In altre parole, al diminuire del valore del momento, il ramo di scarico tende verso l’origine. Per questo motivo, nel presente lavoro è stata valutata l’influenza del comportamento a trazione del calcestruzzo sulla risposta di pareti di controventamento in c.a., integrando una legge di sola compressione (Kent e Park 1971) i risultati sperimentali di Reinhardt (1986, 1989) modificati da Ferracuti e Savoia (2004). All’interno de...

The cyclic laws for dynamic analyses of reinforced concrete (RC) structures usually neglect the c... more The cyclic laws for dynamic analyses of reinforced concrete (RC) structures usually neglect the concrete traction strength and the reloading branch from traction to compression. These assumptions may lead to unreal results in cyclic or dynamic analyses. For example, flag-shaped moment-curvature diagrams of slender RC walls are presented. For this reason, the behaviour of concrete in cyclic tension, determined by Reinhardt et al. [1,2] and modified by Ferracuti and Savoia [3], is added to an existing cyclic stress-strain law. Making use of the finite element (FE) software OpenSees, the resulting concrete law is firstly validated by simulating experimental tests on RC cantilever beams cyclically loaded. Then, slender RC walls in multi-storey buildings are considered and dynamic analyses are done. Moment-curvature curves at base sections are obtained, together with force and displacement envelopes. The results obtained with the implemented law are compared against the ones obtained wit...

La memoria riporta una panoramica degli interventi realizzati dopo la sequenza sismica emiliana d... more La memoria riporta una panoramica degli interventi realizzati dopo la sequenza sismica emiliana del maggio 2012 negli edifici a struttura prefabbricata in c.a. ubicati presso il Polo Scientifico-Tecnologico dell’Università di Ferrara. Gli edifici sono sorti tra il 1996 e il 2002, quando Ferrara non rientrava in zona sismica. Essi hanno pertanto i tegoli di copertura e le travi in semplice appoggio rispettivamente su travi e pilastri, senza alcun dispositivo di ritegno. Non essendo lecito affidare unicamente alla forza d’attrito la resistenza nei confronti delle azioni sismiche, gli edifici sono stati dichiarati inagibili subito dopo la sequenza, pur non avendo riportato danni significativi. Allo scopo di consentirne una rapida riapertura sono state progettate opportune connessioni metalliche. Le forze di progetto da affidare alle connessioni sono state determinate tramite modellazioni degli edifici agli elementi finiti su sono state effettuate analisi dinamiche con spettro di risposta.

Key Engineering Materials, May 11, 2022

Advanced engineering forum, Aug 31, 2022

This is a preliminary study to assess the mechanical behavior of an elevator car frame made of st... more This is a preliminary study to assess the mechanical behavior of an elevator car frame made of steel components, through dynamic identification. Final element models considering different restraint conditions on element nodes are taken into account to evaluate how the whole performance of the structure is affected by local connections.

This paper presents a critical review of several analytical and numerical models that may be adop... more This paper presents a critical review of several analytical and numerical models that may be adopted for studying the out-of-plane behaviour of masonry structures having regular texture, with particular attention to the case of historical masonry, that is characterized by rigid blocks connected by mortar joints modelled as elastic interfaces. Discrete model, Love-Kirchhoff and Reissner-Mindlin plate models and a full three-dimensional heterogeneous finite element model are considered. The elastic parameters of both plate models are based on an existing compatible identification between a three-dimensional discrete model and two-dimensional plate models. Numerical tests are carried on by defining four case studies and paying attention to an in-plane scale factor, representing the size of heterogeneity of the masonry pattern, and to an out-of-plane scale factor, representing the thickness of the structure. Numerical tests show that the existing discrete model is simple and effective for representing masonry behaviour, especially when the magnitude of the heterogeneity is large with respect to the overall size of the panel. Increasing the in-plane scale factor, both plate models converge to the discrete one, but the Reissner-Mindlin plate model shows a better convergence and also allows the adoption of a simple plate finite element for performing numerical analysis

The complexity of multi-leaf masonry walls suggests further researches on the dynamic behaviour m... more The complexity of multi-leaf masonry walls suggests further researches on the dynamic behaviour mainly characterized by incoherent response between the different layers. The intrinsic discontinuity and the manufacturing imperfections are amplified by the incremental damage that triggers different failure mechanisms that affect the dynamic parameters, such as modal shapes, frequencies and damping ratios. The dynamic identification with output only methodology has been proposed in this work on different multi-leaf masonry walls subjected to uniaxial compressive load. The responses of full infill, damaged infill and strengthened infill masonry panels with different widespread damage have been recorded. The evolution of the damage scenario changes the modal shapes, the related frequencies and the damping ratios that through the comparison with the data of the initial conditions can detect the anomalies and then the intrinsic vulnerabilities. Through the curvature modal shape methods and...

Structural stability is a major consideration in the design of structures. The stability is affec... more Structural stability is a major consideration in the design of structures. The stability is affected both by structure dimensions and by geometrical and mechanical imperfections. The intrinsic heterogeneity of historical masonry affects its structural behaviour; the identification of the local homogeneity degradation allows to define a new design approach to take on the structural rehabilitation of multi-leaf masonry structures. In this paper, the imperfection effects on the performances of multi-leaf masonry walls, considered as orthotropic material, are investigated using experimental and numerical approaches based on modal analysis [1, 2]. Unavoidable imperfections of workmanship, emphasized by mechanical orthotropy, affect the application of conventional design approach. After a first identification of the dynamic parameters - such as frequencies and modal shapes, of different multi-leaf masonry panels characterized by undamaged, damaged and strengthened fill - the model updating procedure has been applied to assess the local and global modal shapes. A Finite Element Model has been built simulating the fill by mono-dimensional element with different unidirectional stiffness between the external layers to distinguish and calibrate the local modal shapes and, then, the global response [3, 4]. The experimental and numerical data have been compared to analyse the reliability of the applied method [5]; the calibrated models have been tested through the non-linear static analysis and the results have been compared with the structural performances of the multi-leaf masonry panels subjected to the compressive loads

Most Europeans historical buildings are made by brick or stone masonry, often constituted by mult... more Most Europeans historical buildings are made by brick or stone masonry, often constituted by multiple leaves. A widespread multi-leaf typology is the three-leaf brick masonry wall, which presents two external brick leaves and one inner core consisting of different incoherent materials, with large presence of voids. Brick masonry behaviour tends to brittle failure mechanisms. By reference to solid masonry, multiple leaf walls present a more complex mechanical behaviour, with not simple, but combined collapse mechanisms: their interpretation remains a challenge [1-3]. The literature referred to modelling masonry interface behaviour considers mortar joints reduced to interfaces and internal block interfaces [4]. Here attention is focused on modelling interface between masonry layers: contact relationships between the inner core and the external leaves. This work develops interface models to describe the internal load distribution in a multi-leaf masonry wall, in addition to existing models already adopted for one-leaf masonry elements [5]. Compressive load results are evaluated with reference to experimental data recently obtained by the research group [6] by means of tests carried out at Laboratorio di Scienza delle Costruzioni IUAV (Labsco). This investigation aims to develop a suitable approach to predict the performance of historical masonry wall by FE & DE simulations. Here the two numerical modelling strategies on three-leaf brick masonry walls are presented and compared. References [1] Binda, L., Pina-Henriques, J., Anzani, A., Fontana, A., Louren\ue7o, P.B., \u201cA contribution for the understanding of load-transfer mechanisms in multi-leaf masonry walls: testing and modelling\u201d, Engineering Structures, 28(8), pp. 1132\u20131148 (2006). [2] Ramalho, M.A., Taliercio, A, Anzani, A., Binda, L. Papa, E., \u201cA numerical model for the description of the nonlinear behaviour of multi-leaf masonry walls\u201d, Advances in Engineering Software, 39(4), pp. 249-257 (2008). [3] Milani, G., \u201c3D upper bound limit analysis of multi-leaf masonry walls\u201d, International Journal of Mechanical Sciences, 50(4), pp. 817-836 (2008). [4] Louren\ue7o, P.B., Rots, J.G., \u201cA multi-surface interface model for the analysis of masonry structures\u201d, ASCE Journal of Engineering Mechanics, 123(7), pp. 660\u2013668 (1997). [5] Baraldi, D., Reccia, E., Cecchi, A., \u201cIn plane loaded masonry walls: DEM and FEM/DEM models. A critical review\u201d, Meccanica, 53, pp. 1613\u20131628 (2018). [6] Boscato, G., Reccia, E., Cecchi, A., \u201cNon-destructive experimentation: Dynamic identification of multi-leaf masonry walls damaged and consolidated\u201d, Composites Part B: Engineering, 133, pp. 145\u2013165 (2018)

International Journal of Solids and Structures, 2021

Composites: Mechanics, Computations, Applications: An International Journal, 2019

Nonlinear behavior of masonry panels is a topic of great interest in the civil engineering and ar... more Nonlinear behavior of masonry panels is a topic of great interest in the civil engineering and architecture fields. Several numerical approaches may be found in the literature. Here, three different models are presented and compared to investigate nonlinear behavior of in-plane loaded masonry walls: Discrete Element (DE) model, combined Finite/Discrete Element (FE/DE) model, Finite Element model based on a total rotating strain smeared crack approach (FE-TRSCM). Hence, analysis of masonry is carried out at different scales to compare reliability and application fields of the models. The DE and FE/DE models adopt a micromodeling strategy based on discrete cracks, blocks modeled as independent bodies and mortar joints as elastoplastic Mohr\u2013Coulomb interfaces. These approaches already turned out to be in good agreement for in-plane nonlinear analysis. Here, the FE/DE model adopts hypothesis of infinitely resistant and deformable blocks, with cracks occurring only along mortar joints. Deformability is assumed in the triangular FE domain discretization and embedded crack elements may be activated whether tensile or shear strength is reached. The FE-TRSCM follows a macromodeling approach based on the smeared crack theory, often adopted for concrete. Masonry is modeled as a homogeneous material, with a yield criterion based on fracture energy accounting for masonry softening response on compression and tension. Three approaches are compared and calibrated by reproducing experimental tests on masonry panels in compression and under an increasing shear action. The parametric analyses show the capacity and limit of local micromodels or continuous diffused model to represent masonry behavior

Composite Structures, 2016

Abstract The research presented herein aimed to simulate the structural behavior of laminated gla... more Abstract The research presented herein aimed to simulate the structural behavior of laminated glass with all the glass layers broken, by means of the discrete element modeling. This paper focuses on laminated glass composed of two layers made of tempered glass and an interlayer made of either a totally compliant or a relatively stiff material. The paper demonstrates that discrete element modeling is a viable tool to predict the load–deflection curve from the cracking up to the collapse of laminated glass members, and, hence, to assess the collapse limit states of structural glass. In fact, discrete element modeling may simulate the non-linear composite behavior that the polymeric interlayer and the glass fragments provide a member with, considering the crack patterns of the broken glass, the visco-elasticity of the interlayer, and the structural conditions of the member. The validity of the method is also confirmed through comparisons with other sources — namely, some experiments performed by the authors and an empirical model. The paper presents the method and the results from its application to typical laminated glass members used for structural glass. Those results provide insight into the effects of the design choices on the post-breakage behavior; emphasis is placed on the role played by the type of interlayer.

Proceedings of the Fifteenth International Conference on Civil, Structural and Environmental Engineering Computing

In this paper a free modal analysis for the Frari historical bell tower in Venice is described. T... more In this paper a free modal analysis for the Frari historical bell tower in Venice is described. Three-dimensional finite element models and an analytical model are proposed. The proposal is to evaluate the sensitivity of the models to several geometric parameters, i.e. geometric irregularities, the presence of openings, different thicknesses of external walls. With this aim four models are proposed: i) a model of external and internal walls with real geometric parameters; ii) a model of the only external walls with real geometric parameters; iii) a simplified model of external and internal walls represented as a rectangular girder; iv) a simplified model of the only external walls represented as rectangular girder. The analytical simplified model is proposed as a comparative example. The analysis shows interesting results: i) frequencies are strongly connected to the internal nucleus; ii) mass participation is not uncoupled and always are present both flexural and torsional mode, due to geometric non-alignment to the vertical axis. Geometric irregularities entail only a part of the whole mass, which is involved in the flexural mode, while a torsional component is entailed into the mass participation. This changes entire structural behaviour. For this reasons, dynamic analysis must take into account actual geometry: effective thickness related to mass distribution, opening presence and vertical inclination

The use of refined models for investigating the in-plane behaviour of periodic brickwork is an ac... more The use of refined models for investigating the in-plane behaviour of periodic brickwork is an active field of research; here a comparison between a Discrete Element Method (DEM) and a Finite Element/Discrete Element Method (FEM/DEM) is performed.

European Journal of Mechanics - A/Solids, 2015

This contribution presents a simple and effective numerical model for performing static analyses ... more This contribution presents a simple and effective numerical model for performing static analyses of beams in frictionless and bilateral contact with a three-dimensional (3D) elastic and isotropic half-space. Such a problem can suitably represent the behaviour of strip footings and shallow foundations in building structures. A coupled finite element-boundary integral equation (FE-BIE) method, already introduced for beams on half-plane [1], is here extended to the case of beams on 3D half-space, by adopting a mixed variational formulation which assumes as independent fields both beam displacements, rotations and contact surface tractions. Mixed formulation includes the Green function of the 3D half-space [2]. The resulting numerical model makes use of locking-free \u201cmodified\u201d Hermitian shape functions [3] for the beam and piecewise constant function for the substrate tractions. For this purpose, only the contact surface underneath the foundation needs to be discretized with rectangular elements; furthermore, traction distribution in beam transverse direction is considered with an adequate mesh refinement of contact surface in both plane directions. Numerical tests of both Euler-Bernoulli and Timoshenko beams subject to several load conditions are dealt with. Results in terms of displacements, contact tractions and bending moment are obtained, showing the effectiveness of the model and its convergence to existing analytical and numerical solutions [4]. References [1] Tullini, N., Tralli, A., \u201cStatic analysis of Timoshenko beam resting on elastic half-plane based on the coupling of locking-free finite elements and boundary integral\u201d, Computational Mechanics, 45(2\u20133) pp. 211\u2013225 (2010). [2] Johnson, K.L., Contact mechanics, Cambridge University Press, Cambridge (1985). [3] Reddy, J.N., \u201cOn locking-free shear deformable beam finite elements\u201d, Computer Methods in Applied Mechanics and Engineering, 149(1-4), pp. 113\u2013132 (1997). [4] Biot, M.A., \u201cBending of an infinite beam on an elastic foundation\u201d, Journal of Applied Mechanics, 4, pp. A1\u2013A7 (1937)